Thermal analysis plays a key role in the online inspection of molten iron quality.Different solidification process of molten iron can be reflected by thermal analysis curves,and silicon is one of important elements af...Thermal analysis plays a key role in the online inspection of molten iron quality.Different solidification process of molten iron can be reflected by thermal analysis curves,and silicon is one of important elements affecting the solidification of molten iron.In this study,FeSi75 was added in one chamber of the dual-chamber sample cup,and the influences of FeSi75 additive on the characteristic values of thermal analysis curves and vermiculating rate were investigated.The results show that with the increase of FeSi75,the start temperature of austenite formation TALfirstly decreases and then increases,but the start temperature of eutectic growth TSEF,the lowest eutectic temperature TEU,temperature at maximum eutectic reaction rate TEM,and highest eutectic temperature TERkeep always an increase.The temperature at final solidification point TEShas little change.The FeSi75 additive has different influences on the vermiculating rate of molten iron with different vermiculation,and the vermiculating rate increases for lower vermiculation molten iron while decreases for higher one.According to the thermal analysis curves obtained by a dual-chamber sample cup with 0.30wt.%FeSi75 additive in one chamber,the vermiculating rate of molten iron can be evaluated by comparing the characteristic values of these curves.The time differenceΔtERcorresponding to the highest eutectic temperature TERhas a closer relationship with the vermiculating rate,and a parabolic regression curve between the time differenceΔtERand vermiculating rateηhas been obtained within the range of 65%to 95%,which is suitable for the qualified melt.展开更多
The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Aut...The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Autodesk Inventor 2017 software. The modelled piston was then imported into Ansys for further analysis. Static structural and thermal analysis were carried out on the pistons of the four different materials namely: Al 413 alloy, Al 384 alloy, Al 390 alloy and Al332 alloy to determine the total deformation, equivalent Von Mises stress, maximum shear stress, and the safety factor. The results of the study revealed that, aluminium 332 alloy piston deformed less compared to the deformations of aluminium 390 alloy piston, aluminium 384 alloy piston and aluminium 413 alloy piston. The induced Von Mises stresses in the pistons of the four different materials were found to be far lower than the yield strengths of all the materials. Hence, all the selected materials including the implementing material have equal properties to withstand the maximum gas load. All the selected materials were observed to have high thermal conductivity enough to be able to withstand the operating temperature in the engine cylinders.展开更多
Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings(TBCs),to simplify the modeling process and improve the calculation efficiency.The results sho...Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings(TBCs),to simplify the modeling process and improve the calculation efficiency.The results show that the virtualwall thickness method can improve themesh quality by 20%,reduce the number ofmeshes by 76.7%and save the calculation time by 35.5%,compared with the traditional real wall thickness method.The average calculation error of the two methods is between 0.21%and 0.93%.Furthermore,the temperature at the blade leading edge is the highest and the average temperature of the blade pressure surface is higher than that of the suction surface under a certain service condition.The blade surface temperature presents a high temperature at both ends and a low temperature in themiddle height when the temperature of incoming gas is uniformand constant.The thermal insulation effect of TBCs is the worst near the air film hole,and the best at the blade leading edge.According to the calculated temperature field of the substrate-coating system,the highest thermal insulation temperature of the TC layer is 172.01 K,and the thermal insulation proportions of TC,TGO and BC are 93.55%,1.54%and 4.91%,respectively.展开更多
The connecting rod is one of the most important moving components in an internal combustion engine. The present work determined the possibility of using aluminium alloy 7075 material to design and manufacture a connec...The connecting rod is one of the most important moving components in an internal combustion engine. The present work determined the possibility of using aluminium alloy 7075 material to design and manufacture a connecting rod for weight optimisation without losing the strength of the connecting rod. It considered modal and thermal analyses to investigate the suitability of the material for connecting rod design. The parameters that were considered under the modal analysis were: total deformation, and natural frequency, while the thermal analysis looked at the temperature distribution, total heat flux and directional heat flux of the four connecting rods made with titanium alloy, grey cast iron, structural steel and aluminium 7075 alloy respectively. The connecting rod was modelled using Autodesk inventor2017 software using the calculated parameters. The steady-state thermal analysis was used to determine the induced heat flux and directional heat flux. The study found that Aluminium 7075 alloy deformed more than the remaining three other materials but has superior qualities in terms of vibrational natural frequency, total heat flux and lightweight compared to structural steel, grey cast iron and titanium alloy.展开更多
Micro-thermal analysis (μ-TA), with a miniaturized thermo-resistive probe, allows topographic and thermal imaging of surfaces to be carried out and permits localized thermal analysis of materials. In order to estimat...Micro-thermal analysis (μ-TA), with a miniaturized thermo-resistive probe, allows topographic and thermal imaging of surfaces to be carried out and permits localized thermal analysis of materials. In order to estimate the effective volume of material thermally affected during this localized measurement, simulations, using finite element method were used. Several parameters and conditions were considered. So, thermal conductivity was found to be the driving physical parameter in thermal exchanges. Indeed, the evolution of the heat affected zone (HAZ) versus thermal conductivity can well be described by a linear interpolation. Therefore it is possible to estimate the HAZ before experimental measurements. This result is an important progress especially for accurate interphase characterization in heterogeneous materials.展开更多
Binary orotic acid metal complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), and two mixed metals complexes of (Co(II), Ni(II)) and (Ni(II), Cu(II)) were synthesized and characterized by elemental an...Binary orotic acid metal complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), and two mixed metals complexes of (Co(II), Ni(II)) and (Ni(II), Cu(II)) were synthesized and characterized by elemental analysis, IR, electronic spectra, magnetic susceptibility, and ESR spectra. The Analysis proved that the ligand has different coordination modes and the complexes were of octahedral, tetrahedral, and trigonal bipyramidal geometries. Molecular modeling techniques and quantum chemical methods have been performed for orotic acid to calculate charges, bond lengths, bond angles, dihedral angles, electronegativity (χ), chemical potential (μ), global hardness (η), softness (σ) and the electrophilicity index (ω). The thermal decomposition of the complexes was monitored by TGA, DTA, and DSC techniques under the N2 atmosphere. The thermal decomposition mechanisms of the complexes were suggested. The biological activity of orotic acid and some of the complexes are tested against antibacterial and antifungal organisms.展开更多
<span style="font-family:Verdana;">Laser surface hardening is becoming one of the most successful heat treatment processes for improving wear and fatigue properties of steel parts. In this process, the...<span style="font-family:Verdana;">Laser surface hardening is becoming one of the most successful heat treatment processes for improving wear and fatigue properties of steel parts. In this process, the heating system parameters and the material properties have important effects on the achieved hardened surface characteristics. The control of these variables using predictive modeling strategies leads to the desired surface properties without following the fastidious trial and error method. However, when the dimensions of the surface to be treated are larger than the cross section of the laser beam, various laser scanning patterns can be used. Due to their effects on the hardened surface properties, the attributes of the selected scanning patterns become significant variables in the process. This paper presents numerical and experimental investigations of four scanning patterns for laser surface hardening of AISI 4340 steel. The investigations are based on exhaustive modelling and simulation efforts carried out using a 3D finite element thermal analysis and structured experimental study according to Taguchi method. The temperature distribution and the hardness profile attributes are used to evaluate the effects of heating parameters and patterns design parameters on the hardened surface characteristics. This is very useful for integrating the scanning patterns</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">’</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> features in an efficient predictive modeling approach. A structured experimental design combined to improved statistical analysis tools </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> used</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> to</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> assess the 3D model performance. The experiments are performed on a 3 kW Nd:Yag laser system. The modeling results exhibit a great agreement between the predicted and measured values for the hardened surface characteristics. The model evaluation reveal</span></span></span><span><span><span>s </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">also its ability to provide not only accurate and robust predictions of the temperature distribution and the hardness profile as well an in-depth analysis of the effects of the process parameters.</span></span></span>展开更多
In order to study the internal temperature changes and heat transfer phenomena of a model during external warming, a heat transfer simulation was conducted. The thermal analysis of the model was simulated by using ANS...In order to study the internal temperature changes and heat transfer phenomena of a model during external warming, a heat transfer simulation was conducted. The thermal analysis of the model was simulated by using ANSYS/LSDYNA software, and the heat and heat transfer phenomena of the warhead in the actual process were simulated by setting the temperature conditions on the surface of the model, and the model boundary and internal temperature changes were obtained from the simulation experiments, and relevant conclusions were drawn.展开更多
In order to better understand the thermodynamic properties of magnesium oxysulfate(MOS)cement,pure reagent was analyzed to prepare magnesium sulfide cement,non-isothermal kinetics calculation of the main hydration pro...In order to better understand the thermodynamic properties of magnesium oxysulfate(MOS)cement,pure reagent was analyzed to prepare magnesium sulfide cement,non-isothermal kinetics calculation of the main hydration products was also carried out,and the conversion process of magnesium sulfide cement 517 phase at different temperatures was investigated.Composition of magnesium sulfide cement prepared was measured by XRD technique,and decomposed by a comprehensive thermal analyzer,and DSC curves of magnesium sulfide cement under different temperature rising rates were processed by Kinssinger method and Dolye-Ozawa method.According to the TG-DSC curves of magnesium sulfide cement,the thermal decomposition reaction process can be divided into five stages under normal conditions.The DSC curve was processed by Kinssinger method and Dolye-Ozawa method,and the kinetic analysis was carried out to calculate the 517 phase activation energy of magnesium sulfide cement.The three stages correspond to different activation energies.Therefore,flame retardant mechanism and thermal decomposition mechanism of magnesium sulfide cement based materials are deduced.展开更多
Quantitative prediction of phase content is of great importance to control and optimize the heat treat-ment process of steels.In this work,a model for predicting the phase content of tempered high carbon steels was pr...Quantitative prediction of phase content is of great importance to control and optimize the heat treat-ment process of steels.In this work,a model for predicting the phase content of tempered high carbon steels was proposed by taking a martensitic 100Cr6 bearing steel as a model case.The microstructural transformations during tempering were studied using thermal analysis,transmission electron microscopy(TEM),and X-ray diffraction(XRD).Kinetics analysis of thermal evolution by employing the isoconver-sional method,and assisted by TEM and XRD characterization,were performed to quantitatively estimate the volume fractions of different phases after tempering.A series of isothermal tempering experiments were designed to verify the model.The predicted results were in good agreement with the experimental results of XRD and electrolytic extraction measurements.展开更多
In the 21st century, the deployment of ground-based Solar Photovoltaic (PV) Modules has seen exponential growth, driven by increasing demands for green, clean, and renewable energy sources. However, their usage is con...In the 21st century, the deployment of ground-based Solar Photovoltaic (PV) Modules has seen exponential growth, driven by increasing demands for green, clean, and renewable energy sources. However, their usage is constrained by certain limitations. Notably, the efficiency of solar PV modules on the ground peaks at a maximum of 25%, and there are concerns regarding their long-term reliability, with an expected lifespan of approximately 25 years without failures. This study focuses on analyzing the thermal efficiency of PV Modules. We have investigated the temperature profile of PV Modules under varying environmental conditions, such as air velocity and ambient temperature, utilizing Computational Fluid Dynamics (CFD). This analysis is crucial as the efficiency of PV Modules is significantly impacted by changes in the temperature differential relative to the environment. Furthermore, the study highlights the effect of airflow over solar panels on their temperature. It is found that a decrease in the temperature of the PV Module increases Open Circuit Voltage, underlining the importance of thermal management in optimizing solar panel performance.展开更多
Thermal analysis of data centers is in urgent need to ensure that computer chips remain below the critical temperature while the energy consumption for cooling can be reduced.It is difficult to obtain detailed hotspot...Thermal analysis of data centers is in urgent need to ensure that computer chips remain below the critical temperature while the energy consumption for cooling can be reduced.It is difficult to obtain detailed hotspot locations and temperatures of chips in large data centers containing hundreds of racks or more by direct measurement.In this paper,a multi-scale thermal analysis method is proposed that can predict the temperature distribution of chips and solder balls in data centers.The multi-scale model is divided into six scales:room,rack,server,Insulated-Gate Bipolar Transistor(IGBT),chip and solder ball.A concept of sub-model is proposed and the six levels are organized into four simulation sub-models.Sub-model 1 contains Room,Rack and Server(RRS);Sub-model 2 contains Server and IGBT(SI);Sub-model 3 contains IGBT and Chip(IC),and Sub-model 4 contains Chip and Solder-ball(CS).These four sub-models are one-way coupled by transmitting their results as boundary conditions between levels.The full-field simulation method is employed to verify the efficiency and accuracy of multi-scale simulation method for a single-rack data center.The two simulation results show that the highest temperature emerges in the same location.The Single-rack Full-field Model(SRFFM)costs 2.5 times more computational time than that with Single-rack Multi-scale Model(SRMSM).The deviation of the highest temperature of chips and solder balls are 1.57℃and 0.2℃between the two models which indicates that the multi-scale simulation method has good prospect in the data center thermal simulation.Finally,the multi-scale thermal analysis method is applied to a ship data center with 15 racks.展开更多
Thermal properties, as well as the dynamic mechanical behavior of recycled polypropylene composites with vegetal leaves contents, were studied by thermal analysis techniques: TG/DTG, DTA, and DMA. Composites made of p...Thermal properties, as well as the dynamic mechanical behavior of recycled polypropylene composites with vegetal leaves contents, were studied by thermal analysis techniques: TG/DTG, DTA, and DMA. Composites made of polypropylene recycled with 1%, 5%, 10%, and 15% ww?1 vegetal leaves were prepared using the melt blending technique. The results revealed that the viscoelastic properties were influenced by fiber content;however, the glass transition temperature (Tg) of the composite did not show significant changes to the fiber content. In the end, the composite with 5% of palm leaves and PP recycled presented the most promising results since this one kept the solid characteristic on the dynamic mechanical properties. This work presents an environmental friendly alternative to manage natural waste, also being a form of reducing polymeric materials waste.展开更多
Thermal properties such as melting temperature can well reflect the microstructure of the polymer material, and have practical implications in the application of nanofibers. In this work, we investigated the melting t...Thermal properties such as melting temperature can well reflect the microstructure of the polymer material, and have practical implications in the application of nanofibers. In this work, we investigated the melting temperature of individual electrospun poly(vinylidene fluoride)(PVDF) nanofibers with diameters ranging from smaller than 200 nm to greater than 2 μm by the local thermal analysis technique. The PVDF fibers obtained under four different conditions were found to crystallize into α and β phases, and the fiber mats showed typical values in the crystallinity and Tm with no significant difference among the four. However, analyses at single fiber level revealed broad distribution in diameter and Tm for the fibers produced under identical electrospinning condition. The Tm of individual nanofibers was found to remain constant at large diameters and increase quickly when reducing the fiber diameter toward the nanoscale, and Tm values of 220-230 ℃ were observed for the thinnest nanofibers, much higher than the typical values reported for bulk PVDF. The Tm and molecular orientation at different positions along a beaded fiber were analyzed, showing a similar distribution pattern with a minimum at the bead center and higher values when moving toward both directions. The results indicate that molecular orientation is the driving mechanism for the observed correlation between the Tm and the diameter of the nanofibers.展开更多
The large fire door is the key component to ensure the effectiveness of fire zone in AP1000 nuclear reactor.According to the fire design requirements and design criteria,the global structure of the large fire door is ...The large fire door is the key component to ensure the effectiveness of fire zone in AP1000 nuclear reactor.According to the fire design requirements and design criteria,the global structure of the large fire door is designed.Based on the designed structure,the thermal mathematical model of the large fire door is established.Based on the solid heat transfer theory,the multi-layer heat transfer theory and integrated heat transfer theory,the differential equations of heat conduction,initial conditions,and boundary conditions are determined.Thermal analysis for the fire door leaf and the closure is carried out by using the method of numerical simulation.Results show that:considering the thermal load,the whole structure of the large fire door can meet the fire resistance limit of 3 hours and the design is reasonable and feasible.This study provides theory basis for the design of the large fire door.展开更多
Compact stator structure of flux switching machines(FSMs)encompassing both permanent magnets(PMs)and armature winding slots(AWS)attract research interest whenever high power and density are the basic requirements.Howe...Compact stator structure of flux switching machines(FSMs)encompassing both permanent magnets(PMs)and armature winding slots(AWS)attract research interest whenever high power and density are the basic requirements.However,it also results in temperature rises owing to heat generation by electromagnetic power losses degrading the electromagnetic performance and affecting machine performance.In this study,a segmented permanent magnet(SPM)consequent pole FSM(SPM-CPFSM)is developed,which provides a stator cooling channel(duct)for improved heat dissipation to avoid demagnetization of PM as well as overheating.Furthermore,this study investigates detailed electromagnetic performance analysis and prediction of temperature variation in various machine parts owing to the heat generated by iron,copper,and magnet eddy current losses utilizing coupled electromagnetic-thermal analysis accounting for magnetic flux density variation.In comparison with the 2D analysis,the developed 3D coupled-field analysis more accurately predicts electromagnetic performance and temperature distribution.Analysis reveals that a cooling duct at the stator significantly assists in stator heat dissipation in the axial direction ensuring a safe operating condition of the PMs as well as machine parts to avoid overheating.展开更多
China’s first 35 kJ high temperature superconducting magnetic energy storage(SMES)system with an experiment equipment was depicted.The dynamic heat analysis of the magnet of the SMES was conducted through the current...China’s first 35 kJ high temperature superconducting magnetic energy storage(SMES)system with an experiment equipment was depicted.The dynamic heat analysis of the magnet of the SMES was conducted through the current load test on the directly cooled conduction magnet.The research results were as follows:when the converter charges and discharges the magnet for energy storage,the hysteresis loss is the main part of power loss,and contributes significantly to temperature rise;reducing the current frequency at the side of direct current is conducive to restraining temperature rise.The optimizing factors of the cool-guide structure were analyzed based on the heat stability theory,and it was found that the heat transfer of its key part(at the top of the magnet)must be strengthened to reduce the axial temperature difference of the magnet.展开更多
A detailed sensitivity study was carried out on various key parameters from a high precision numerical model of a microelectronic package cooled by natural convection, to provide rules for the thermal modeling of micr...A detailed sensitivity study was carried out on various key parameters from a high precision numerical model of a microelectronic package cooled by natural convection, to provide rules for the thermal modeling of microelectronic packages subjected to natural convection heat transfer. An accurate estimate of the junction temperature, with an error of less than 1˚C, was obtained compared to the experimental data for the vertical and horizontal orientations of the test vehicle in the JEDEC Still Air configuration. The sensitivity study showed that to have an accurate estimate of the temperature, the following elements should be present in the thermal model: radiation heat transfer in natural convection cooling;a computational fluid dynamics analysis to find realistic convection coefficients;detailed models of the high conductivity elements in the direction of the heat flow towards the environment;and finally precise values for the thicknesses of layers and the thermal properties of the substrate and the printed circuit board.展开更多
In this study,to better understand the reaction mechanism between inorganic salts and nitrocellulose,CaCO_(3) and Li_(2)CO_(3) were evaluated with respect to their effects on the thermal degradation of NC in nitrogen ...In this study,to better understand the reaction mechanism between inorganic salts and nitrocellulose,CaCO_(3) and Li_(2)CO_(3) were evaluated with respect to their effects on the thermal degradation of NC in nitrogen atmosphere using TG/DSC at three different heating rates(2,5,10 K/min).The numerical relationship between activation energy(E)and conversion rate was obtained by FWO and KAS method,and it was discovered that CaCO_(3) could improve the thermal stability of NC.Activation energy values were calculated by Kissinger method,and it was found that NC that contain Li2CO3had the highest activation energy while NC containing CaCO3had the lowest E value.By combining the thermal analysis data with Malek method,the most probable mechanism model of thermal degradation is obtained as Sesták-Berggren model,which expression is f(α)=α^(m)(1-α)^(n).As a result of this study,there are certain guiding principles that can be applied to the pyrolysis reaction model and to the actual production process of nitrocellulose.展开更多
In modern metallurgical industry,microwave thermal technique has many advantages as one efficient energy treatment in an electromagnetic form,such as internal self-generated heat,easy access to control a volumetric he...In modern metallurgical industry,microwave thermal technique has many advantages as one efficient energy treatment in an electromagnetic form,such as internal self-generated heat,easy access to control a volumetric heating process,and consensus on cleanliness,convenience and high efficiency of energy use.Both permittivity and permeability of molybdenite concentrate were measured for a further discussion about its electromagnetic heating coupling.A bidirectional coupling physics field in numerical modeling was undertaken to evaluate the microwave absorption potential and dielectric heating performance of molybdenite concentrate by the multi-physics finite element method.The electromagnetic morphology and the field distribution strength were described in the microwave reaction cavity.The electromagnetic field strength and the dissipation coefficient induced by temperature variation were represented throughout the whole heat chamber and at key parts of interest.Dependent temperature distribution was compared with that being obtained from a scenario by thermal conduction with a stable heat source.The molybdenite concentrate would be heated at surrounding temperature up to 593℃for 10 min by microwave energy that was transmitted by a rectangular waveguide.Scanning electron microscopy(SEM)patterns suggested that the polished and neat crystalline molybdenum trioxide(MoO_(3))products were achieved by the microwave heating process.The superiority via utilizing microwave thermal technique is expounded in the preparation strategy for molybdenum oxide or molybdenum metal.展开更多
基金the financial support of the State Key Laboratory of Engine Reliability(skler-202105)。
文摘Thermal analysis plays a key role in the online inspection of molten iron quality.Different solidification process of molten iron can be reflected by thermal analysis curves,and silicon is one of important elements affecting the solidification of molten iron.In this study,FeSi75 was added in one chamber of the dual-chamber sample cup,and the influences of FeSi75 additive on the characteristic values of thermal analysis curves and vermiculating rate were investigated.The results show that with the increase of FeSi75,the start temperature of austenite formation TALfirstly decreases and then increases,but the start temperature of eutectic growth TSEF,the lowest eutectic temperature TEU,temperature at maximum eutectic reaction rate TEM,and highest eutectic temperature TERkeep always an increase.The temperature at final solidification point TEShas little change.The FeSi75 additive has different influences on the vermiculating rate of molten iron with different vermiculation,and the vermiculating rate increases for lower vermiculation molten iron while decreases for higher one.According to the thermal analysis curves obtained by a dual-chamber sample cup with 0.30wt.%FeSi75 additive in one chamber,the vermiculating rate of molten iron can be evaluated by comparing the characteristic values of these curves.The time differenceΔtERcorresponding to the highest eutectic temperature TERhas a closer relationship with the vermiculating rate,and a parabolic regression curve between the time differenceΔtERand vermiculating rateηhas been obtained within the range of 65%to 95%,which is suitable for the qualified melt.
文摘The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Autodesk Inventor 2017 software. The modelled piston was then imported into Ansys for further analysis. Static structural and thermal analysis were carried out on the pistons of the four different materials namely: Al 413 alloy, Al 384 alloy, Al 390 alloy and Al332 alloy to determine the total deformation, equivalent Von Mises stress, maximum shear stress, and the safety factor. The results of the study revealed that, aluminium 332 alloy piston deformed less compared to the deformations of aluminium 390 alloy piston, aluminium 384 alloy piston and aluminium 413 alloy piston. The induced Von Mises stresses in the pistons of the four different materials were found to be far lower than the yield strengths of all the materials. Hence, all the selected materials including the implementing material have equal properties to withstand the maximum gas load. All the selected materials were observed to have high thermal conductivity enough to be able to withstand the operating temperature in the engine cylinders.
基金supported by the National Science and Technology Major Project(J2019-IV-0003-0070)the National Natural Science Foundation of China(Grant No.12102320)+1 种基金the Advanced Aviation Power Innovation Workstation Project(HKCX2019-01-003)China Postdoc-toral Science Foundation(2021M692571).
文摘Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings(TBCs),to simplify the modeling process and improve the calculation efficiency.The results show that the virtualwall thickness method can improve themesh quality by 20%,reduce the number ofmeshes by 76.7%and save the calculation time by 35.5%,compared with the traditional real wall thickness method.The average calculation error of the two methods is between 0.21%and 0.93%.Furthermore,the temperature at the blade leading edge is the highest and the average temperature of the blade pressure surface is higher than that of the suction surface under a certain service condition.The blade surface temperature presents a high temperature at both ends and a low temperature in themiddle height when the temperature of incoming gas is uniformand constant.The thermal insulation effect of TBCs is the worst near the air film hole,and the best at the blade leading edge.According to the calculated temperature field of the substrate-coating system,the highest thermal insulation temperature of the TC layer is 172.01 K,and the thermal insulation proportions of TC,TGO and BC are 93.55%,1.54%and 4.91%,respectively.
文摘The connecting rod is one of the most important moving components in an internal combustion engine. The present work determined the possibility of using aluminium alloy 7075 material to design and manufacture a connecting rod for weight optimisation without losing the strength of the connecting rod. It considered modal and thermal analyses to investigate the suitability of the material for connecting rod design. The parameters that were considered under the modal analysis were: total deformation, and natural frequency, while the thermal analysis looked at the temperature distribution, total heat flux and directional heat flux of the four connecting rods made with titanium alloy, grey cast iron, structural steel and aluminium 7075 alloy respectively. The connecting rod was modelled using Autodesk inventor2017 software using the calculated parameters. The steady-state thermal analysis was used to determine the induced heat flux and directional heat flux. The study found that Aluminium 7075 alloy deformed more than the remaining three other materials but has superior qualities in terms of vibrational natural frequency, total heat flux and lightweight compared to structural steel, grey cast iron and titanium alloy.
文摘Micro-thermal analysis (μ-TA), with a miniaturized thermo-resistive probe, allows topographic and thermal imaging of surfaces to be carried out and permits localized thermal analysis of materials. In order to estimate the effective volume of material thermally affected during this localized measurement, simulations, using finite element method were used. Several parameters and conditions were considered. So, thermal conductivity was found to be the driving physical parameter in thermal exchanges. Indeed, the evolution of the heat affected zone (HAZ) versus thermal conductivity can well be described by a linear interpolation. Therefore it is possible to estimate the HAZ before experimental measurements. This result is an important progress especially for accurate interphase characterization in heterogeneous materials.
文摘Binary orotic acid metal complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), and two mixed metals complexes of (Co(II), Ni(II)) and (Ni(II), Cu(II)) were synthesized and characterized by elemental analysis, IR, electronic spectra, magnetic susceptibility, and ESR spectra. The Analysis proved that the ligand has different coordination modes and the complexes were of octahedral, tetrahedral, and trigonal bipyramidal geometries. Molecular modeling techniques and quantum chemical methods have been performed for orotic acid to calculate charges, bond lengths, bond angles, dihedral angles, electronegativity (χ), chemical potential (μ), global hardness (η), softness (σ) and the electrophilicity index (ω). The thermal decomposition of the complexes was monitored by TGA, DTA, and DSC techniques under the N2 atmosphere. The thermal decomposition mechanisms of the complexes were suggested. The biological activity of orotic acid and some of the complexes are tested against antibacterial and antifungal organisms.
文摘<span style="font-family:Verdana;">Laser surface hardening is becoming one of the most successful heat treatment processes for improving wear and fatigue properties of steel parts. In this process, the heating system parameters and the material properties have important effects on the achieved hardened surface characteristics. The control of these variables using predictive modeling strategies leads to the desired surface properties without following the fastidious trial and error method. However, when the dimensions of the surface to be treated are larger than the cross section of the laser beam, various laser scanning patterns can be used. Due to their effects on the hardened surface properties, the attributes of the selected scanning patterns become significant variables in the process. This paper presents numerical and experimental investigations of four scanning patterns for laser surface hardening of AISI 4340 steel. The investigations are based on exhaustive modelling and simulation efforts carried out using a 3D finite element thermal analysis and structured experimental study according to Taguchi method. The temperature distribution and the hardness profile attributes are used to evaluate the effects of heating parameters and patterns design parameters on the hardened surface characteristics. This is very useful for integrating the scanning patterns</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">’</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> features in an efficient predictive modeling approach. A structured experimental design combined to improved statistical analysis tools </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> used</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> to</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> assess the 3D model performance. The experiments are performed on a 3 kW Nd:Yag laser system. The modeling results exhibit a great agreement between the predicted and measured values for the hardened surface characteristics. The model evaluation reveal</span></span></span><span><span><span>s </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">also its ability to provide not only accurate and robust predictions of the temperature distribution and the hardness profile as well an in-depth analysis of the effects of the process parameters.</span></span></span>
文摘In order to study the internal temperature changes and heat transfer phenomena of a model during external warming, a heat transfer simulation was conducted. The thermal analysis of the model was simulated by using ANSYS/LSDYNA software, and the heat and heat transfer phenomena of the warhead in the actual process were simulated by setting the temperature conditions on the surface of the model, and the model boundary and internal temperature changes were obtained from the simulation experiments, and relevant conclusions were drawn.
基金Fund by the National Natural Science Foundation of China (No.51778101)the General Program (Key Program,Major Research Plan)of National Natural Science Foundation of China+2 种基金the National Key R&D Program (No.2020YFC1909304)the National Program on Key Basic Research Project of Chinathe Joint Fund Project of National Natural Fund of China (U1908227)。
文摘In order to better understand the thermodynamic properties of magnesium oxysulfate(MOS)cement,pure reagent was analyzed to prepare magnesium sulfide cement,non-isothermal kinetics calculation of the main hydration products was also carried out,and the conversion process of magnesium sulfide cement 517 phase at different temperatures was investigated.Composition of magnesium sulfide cement prepared was measured by XRD technique,and decomposed by a comprehensive thermal analyzer,and DSC curves of magnesium sulfide cement under different temperature rising rates were processed by Kinssinger method and Dolye-Ozawa method.According to the TG-DSC curves of magnesium sulfide cement,the thermal decomposition reaction process can be divided into five stages under normal conditions.The DSC curve was processed by Kinssinger method and Dolye-Ozawa method,and the kinetic analysis was carried out to calculate the 517 phase activation energy of magnesium sulfide cement.The three stages correspond to different activation energies.Therefore,flame retardant mechanism and thermal decomposition mechanism of magnesium sulfide cement based materials are deduced.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51605355 and 52104381)the National Key R&D Program of China(No.2020YFA0714900)+2 种基金“111 Project”(No.B17034)the Innovative Research TeamDevelopment Program of Ministry of Education of China(No.IRT_17R83)the China Postdoctoral Science Foundation(No.2021M702539)and the State Key Laboratory for Advanced Metals and Materials.
文摘Quantitative prediction of phase content is of great importance to control and optimize the heat treat-ment process of steels.In this work,a model for predicting the phase content of tempered high carbon steels was proposed by taking a martensitic 100Cr6 bearing steel as a model case.The microstructural transformations during tempering were studied using thermal analysis,transmission electron microscopy(TEM),and X-ray diffraction(XRD).Kinetics analysis of thermal evolution by employing the isoconver-sional method,and assisted by TEM and XRD characterization,were performed to quantitatively estimate the volume fractions of different phases after tempering.A series of isothermal tempering experiments were designed to verify the model.The predicted results were in good agreement with the experimental results of XRD and electrolytic extraction measurements.
文摘In the 21st century, the deployment of ground-based Solar Photovoltaic (PV) Modules has seen exponential growth, driven by increasing demands for green, clean, and renewable energy sources. However, their usage is constrained by certain limitations. Notably, the efficiency of solar PV modules on the ground peaks at a maximum of 25%, and there are concerns regarding their long-term reliability, with an expected lifespan of approximately 25 years without failures. This study focuses on analyzing the thermal efficiency of PV Modules. We have investigated the temperature profile of PV Modules under varying environmental conditions, such as air velocity and ambient temperature, utilizing Computational Fluid Dynamics (CFD). This analysis is crucial as the efficiency of PV Modules is significantly impacted by changes in the temperature differential relative to the environment. Furthermore, the study highlights the effect of airflow over solar panels on their temperature. It is found that a decrease in the temperature of the PV Module increases Open Circuit Voltage, underlining the importance of thermal management in optimizing solar panel performance.
基金supported by the National Natural Science Foundation of China(No.51806167)China Postdoctoral Science Foundation(2017M623166)+1 种基金Science and Technology on Thermal Energy and Power Laboratory Open Foundation of China(No.TPL2017BA004)the Fund of Xi’an Science and Technology Bureau(2019218714SYS002CG024).
文摘Thermal analysis of data centers is in urgent need to ensure that computer chips remain below the critical temperature while the energy consumption for cooling can be reduced.It is difficult to obtain detailed hotspot locations and temperatures of chips in large data centers containing hundreds of racks or more by direct measurement.In this paper,a multi-scale thermal analysis method is proposed that can predict the temperature distribution of chips and solder balls in data centers.The multi-scale model is divided into six scales:room,rack,server,Insulated-Gate Bipolar Transistor(IGBT),chip and solder ball.A concept of sub-model is proposed and the six levels are organized into four simulation sub-models.Sub-model 1 contains Room,Rack and Server(RRS);Sub-model 2 contains Server and IGBT(SI);Sub-model 3 contains IGBT and Chip(IC),and Sub-model 4 contains Chip and Solder-ball(CS).These four sub-models are one-way coupled by transmitting their results as boundary conditions between levels.The full-field simulation method is employed to verify the efficiency and accuracy of multi-scale simulation method for a single-rack data center.The two simulation results show that the highest temperature emerges in the same location.The Single-rack Full-field Model(SRFFM)costs 2.5 times more computational time than that with Single-rack Multi-scale Model(SRMSM).The deviation of the highest temperature of chips and solder balls are 1.57℃and 0.2℃between the two models which indicates that the multi-scale simulation method has good prospect in the data center thermal simulation.Finally,the multi-scale thermal analysis method is applied to a ship data center with 15 racks.
文摘Thermal properties, as well as the dynamic mechanical behavior of recycled polypropylene composites with vegetal leaves contents, were studied by thermal analysis techniques: TG/DTG, DTA, and DMA. Composites made of polypropylene recycled with 1%, 5%, 10%, and 15% ww?1 vegetal leaves were prepared using the melt blending technique. The results revealed that the viscoelastic properties were influenced by fiber content;however, the glass transition temperature (Tg) of the composite did not show significant changes to the fiber content. In the end, the composite with 5% of palm leaves and PP recycled presented the most promising results since this one kept the solid characteristic on the dynamic mechanical properties. This work presents an environmental friendly alternative to manage natural waste, also being a form of reducing polymeric materials waste.
基金financially supported by the National Natural Science Foundation of China (No. 21674118)。
文摘Thermal properties such as melting temperature can well reflect the microstructure of the polymer material, and have practical implications in the application of nanofibers. In this work, we investigated the melting temperature of individual electrospun poly(vinylidene fluoride)(PVDF) nanofibers with diameters ranging from smaller than 200 nm to greater than 2 μm by the local thermal analysis technique. The PVDF fibers obtained under four different conditions were found to crystallize into α and β phases, and the fiber mats showed typical values in the crystallinity and Tm with no significant difference among the four. However, analyses at single fiber level revealed broad distribution in diameter and Tm for the fibers produced under identical electrospinning condition. The Tm of individual nanofibers was found to remain constant at large diameters and increase quickly when reducing the fiber diameter toward the nanoscale, and Tm values of 220-230 ℃ were observed for the thinnest nanofibers, much higher than the typical values reported for bulk PVDF. The Tm and molecular orientation at different positions along a beaded fiber were analyzed, showing a similar distribution pattern with a minimum at the bead center and higher values when moving toward both directions. The results indicate that molecular orientation is the driving mechanism for the observed correlation between the Tm and the diameter of the nanofibers.
基金the support of the National Natural Science Foundation of China (Grant No. 51672241)Jiangsu Science and Technology Plan Project of China (Grant No. BE2016134)+5 种基金the 14th batch High-level Talents Project for "Six Talents Peak" (Grant No. XCL-092)the Province Postdoctoral Foundation of Jiangsu (1501164B)the Technical Innovation Nurturing Foundation of Yangzhou University (2017CXJ024)China Postdoctoral Science Foundation (2016M600447)Yangzhou Innovative Capacity Building Plan Project (YZ2017275)Yangzhou University Science Foundation Project (x20180290)
文摘The large fire door is the key component to ensure the effectiveness of fire zone in AP1000 nuclear reactor.According to the fire design requirements and design criteria,the global structure of the large fire door is designed.Based on the designed structure,the thermal mathematical model of the large fire door is established.Based on the solid heat transfer theory,the multi-layer heat transfer theory and integrated heat transfer theory,the differential equations of heat conduction,initial conditions,and boundary conditions are determined.Thermal analysis for the fire door leaf and the closure is carried out by using the method of numerical simulation.Results show that:considering the thermal load,the whole structure of the large fire door can meet the fire resistance limit of 3 hours and the design is reasonable and feasible.This study provides theory basis for the design of the large fire door.
文摘Compact stator structure of flux switching machines(FSMs)encompassing both permanent magnets(PMs)and armature winding slots(AWS)attract research interest whenever high power and density are the basic requirements.However,it also results in temperature rises owing to heat generation by electromagnetic power losses degrading the electromagnetic performance and affecting machine performance.In this study,a segmented permanent magnet(SPM)consequent pole FSM(SPM-CPFSM)is developed,which provides a stator cooling channel(duct)for improved heat dissipation to avoid demagnetization of PM as well as overheating.Furthermore,this study investigates detailed electromagnetic performance analysis and prediction of temperature variation in various machine parts owing to the heat generated by iron,copper,and magnet eddy current losses utilizing coupled electromagnetic-thermal analysis accounting for magnetic flux density variation.In comparison with the 2D analysis,the developed 3D coupled-field analysis more accurately predicts electromagnetic performance and temperature distribution.Analysis reveals that a cooling duct at the stator significantly assists in stator heat dissipation in the axial direction ensuring a safe operating condition of the PMs as well as machine parts to avoid overheating.
基金supported by the Hi-Tech Research and Development Program of China (No.2002AA306331-4)the National Natural Science Foundation of China (Grant No.51076013)the Research Fund for the Doctoral Program of Higher Education of China (No.200040487039).
文摘China’s first 35 kJ high temperature superconducting magnetic energy storage(SMES)system with an experiment equipment was depicted.The dynamic heat analysis of the magnet of the SMES was conducted through the current load test on the directly cooled conduction magnet.The research results were as follows:when the converter charges and discharges the magnet for energy storage,the hysteresis loss is the main part of power loss,and contributes significantly to temperature rise;reducing the current frequency at the side of direct current is conducive to restraining temperature rise.The optimizing factors of the cool-guide structure were analyzed based on the heat stability theory,and it was found that the heat transfer of its key part(at the top of the magnet)must be strengthened to reduce the axial temperature difference of the magnet.
文摘A detailed sensitivity study was carried out on various key parameters from a high precision numerical model of a microelectronic package cooled by natural convection, to provide rules for the thermal modeling of microelectronic packages subjected to natural convection heat transfer. An accurate estimate of the junction temperature, with an error of less than 1˚C, was obtained compared to the experimental data for the vertical and horizontal orientations of the test vehicle in the JEDEC Still Air configuration. The sensitivity study showed that to have an accurate estimate of the temperature, the following elements should be present in the thermal model: radiation heat transfer in natural convection cooling;a computational fluid dynamics analysis to find realistic convection coefficients;detailed models of the high conductivity elements in the direction of the heat flow towards the environment;and finally precise values for the thicknesses of layers and the thermal properties of the substrate and the printed circuit board.
基金the National Natural Science Foundation of China(NSFC,Grants No.52176114 and 52111530091)Jiangsu Funding Program for Excellent Postdoctoral Talent。
文摘In this study,to better understand the reaction mechanism between inorganic salts and nitrocellulose,CaCO_(3) and Li_(2)CO_(3) were evaluated with respect to their effects on the thermal degradation of NC in nitrogen atmosphere using TG/DSC at three different heating rates(2,5,10 K/min).The numerical relationship between activation energy(E)and conversion rate was obtained by FWO and KAS method,and it was discovered that CaCO_(3) could improve the thermal stability of NC.Activation energy values were calculated by Kissinger method,and it was found that NC that contain Li2CO3had the highest activation energy while NC containing CaCO3had the lowest E value.By combining the thermal analysis data with Malek method,the most probable mechanism model of thermal degradation is obtained as Sesták-Berggren model,which expression is f(α)=α^(m)(1-α)^(n).As a result of this study,there are certain guiding principles that can be applied to the pyrolysis reaction model and to the actual production process of nitrocellulose.
基金Educational Science and Technology Project,Educational Department of Guizhou Province,China(No.2022005)。
文摘In modern metallurgical industry,microwave thermal technique has many advantages as one efficient energy treatment in an electromagnetic form,such as internal self-generated heat,easy access to control a volumetric heating process,and consensus on cleanliness,convenience and high efficiency of energy use.Both permittivity and permeability of molybdenite concentrate were measured for a further discussion about its electromagnetic heating coupling.A bidirectional coupling physics field in numerical modeling was undertaken to evaluate the microwave absorption potential and dielectric heating performance of molybdenite concentrate by the multi-physics finite element method.The electromagnetic morphology and the field distribution strength were described in the microwave reaction cavity.The electromagnetic field strength and the dissipation coefficient induced by temperature variation were represented throughout the whole heat chamber and at key parts of interest.Dependent temperature distribution was compared with that being obtained from a scenario by thermal conduction with a stable heat source.The molybdenite concentrate would be heated at surrounding temperature up to 593℃for 10 min by microwave energy that was transmitted by a rectangular waveguide.Scanning electron microscopy(SEM)patterns suggested that the polished and neat crystalline molybdenum trioxide(MoO_(3))products were achieved by the microwave heating process.The superiority via utilizing microwave thermal technique is expounded in the preparation strategy for molybdenum oxide or molybdenum metal.
